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Noble Gases helium (He) neon (Ne) argon (Ar) krypton (Kr) xenon (Xe) radon (Rn) form group 18 of the periodic table The noble gases

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Text of Noble Gases helium (He) neon (Ne) argon (Ar) krypton (Kr) xenon (Xe) radon (Rn) form group 18...

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  • Noble Gases
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  • helium (He) neon (Ne) argon (Ar) krypton (Kr) xenon (Xe) radon (Rn) form group 18 of the periodic table The noble gases
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  • Noble Gases Minor constituents of the atmosphere Isolated first by Ramsay Fractionation of liquid air Helium occurs in radioactive mineral Radon Radioactive with short half-lives Characterized in the decay series from uranium and thorium Ooccurrence
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  • Noble Gases He 1 s 2 Ne [He] 2 s 2 2 p 6 Ar[Ne] 3 s 2 3 p 6 Kr[Ar] 3 d 10 4 s 2 4 p 6 Xe[Kr] 4 d 10 5 s 2 5 p 6 Rn[Xe] 4 f 14 5 d 10 6 s 2 6 p 6 Electonic Configurations
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  • Noble Gases The stability of the noble gases with respect to loss or acceptance of electrons is due to their high ionization potentials and the highly positive values of their electron affinities. These effects are essentially responsible for the chemical inertness of these elements. The chemical inertness
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  • Noble Gases It was long believed that the noble gases were incapable of forming chemical compounds. In 1962 three groups succeeded independently in preparing noble gas compounds. In June 1962 Bartlett prepared the orange- yellow, moisture-sensitive compound "xenon hexafluoroplatinate" by reaction of Xe with PtF 6. In July 1962 Hoppe obtained the first binary compound of xenon, XeF 2, This was followed one month later by the synthesis of XeF 4 by Claasen, Selig, and Malm. Compounds
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  • Noble Gas A surprising result The valence compounds of krypton and xenon do not involve a new type of chemical bonding. The atoms are bound in the same manner as in the long-known interhalogen compounds, such as IF 7, and in TeF 6. Bonding in Compounds
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  • Noble Gas For the formation of noble gas compounds An electron must be promoted from the p shell to the d shell Formation of bonding electron pairs with another atom can occur with hybridization of the type s p d n (n = 1, 2, 3, 4). Bonding in Compounds
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  • Noble Gas Noble gas compounds can be divided into three general types : Short-lived molecules containing noble gas atoms Valence compounds Inclusion compounds (clathrates and intercalation compounds) Types of Compounds
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  • Noble Gas Valence compounds Only formed with the most electronegative elements (till now, F, Cl, Br, N, and C) Whereby thermodynamically stable compounds with fluorine are formed only by xenon and radon. Types and Stability of Compounds
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  • Noble Gas The thermodynamic stability of noble gas compounds, for example, the halides, follows the following general rules : The stability of the compounds EX 2 increases with increasing atomic number of the noble gas and with decreasing atomic number of the halogen : ArF 2 < KrF 2 < XeF 2 < RnF 2 XeF 2 > XeCl 2 > XeBr 2 The stability of the compounds decreases as the oxidation state of the noble gas increases. Types and Stability of Compounds
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  • Noble Gas Up to now, attempts to react helium, neon, and argon with other elements have failed The chemistry of krypton is limited to the detection of the ions KrF +, Kr 2 F 3 +, KrF 2 radical, and the synthesis of KrF 2 and its complexes KrF 2 2 SbF 5 and KrF 2 x AsF 5. A report of the detection of KrF 4 proved to be erroneous. The existence of a compound with a Kr N bond is claimed Compounds
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  • Noble Gas Compounds of xenon are known in the oxidation states II VIII, some of which are remarkably stable. Xenon (II) fluoride is even commercially available. Compounds
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  • Oxidati on state CompoundFormmp, CStructure IIXeF 2 colorless crystals 129linear IVXeF 4 colorless crystals 117square planar VIXeF 6 colorless VIXeOF 4 colorless liquid 46octahedral VIXeO 3 colorless crystals tetrahedral VI n K + [XeO 3 F ] n colorless crystals qpy F-bridges VIIIXeO 4 colorless gas tetrahedral VIIIXeO 6 4 colorless salt octahedral Table 21-2
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  • Noble Gas Xe + F 2 = XeF 2 400 C, 0.1 M Pa, deficiency of F 2 Xe + 2F 2 = XeF 4 600 C, 0.6 M Pa Xe : F 2 = 1 : 5 Xe + 3F 2 = XeF 6 300 C, 6 M Pa Preparation of Compounds
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  • Noble Gas Hydrolysis XeF 2 + 2OH - = Xe + 1/2O 2 + 2F 2 + H 2 O XeF 4 + 6H 2 O = XeO 3 + 2Xe + 3/2O 2 + 12HF XeF 6 + 3H 2 O = XeO 3 + 6HF Oxidation NaBrO 3 + XeF 2 + 2H 2 O = NaBrO 4 + 2HF + Xe Fluoridation 2XeF 6 + 3SiO 2 = 2XeO 3 + 3SiF 4 Properties of Compounds
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  • Noble Gas The structures of the fluorides, oxyfluorides, and oxides of xenon follow the rules of the valence shell electron pair repulsion model (VSEPR) When the lone pairs are taken into account XeF 2, XeOF 2, and XeO 2 F 2 have trigonal bipyramidal structures with a linear F Xe F axis in the gas phase. Molecular Structures of Compounds
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  • Noble Gas In XeF 4 and its oxyfluorides, the four fluorine atoms occupy equatorial positions, while the electron lone pairs or oxygen atoms occupy the axial positions of the octahedral structure. Molecular Structures of Compounds
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  • Molecular structure of XeF 6 A) In the gas phase : dynamic, distorted octahedral ;
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  • Molecular structure of XeF 6 B) In solution : In nonbridging solvents (CF 2 Cl 2, CF 3 Cl, SO 2 ClF, F 5 SOSF 5 ), XeF 6 forms Xe 4 F 24 tetramers by fluoride bridging, and perhaps also through weak Xe Xe interactions. The 24 F atoms are magnetically equivalent, suggesting that they are involved in a rearrangement process ;
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  • Molecular structure of XeF 6 C) In the crystal : The tetrameric Xe 4 F 24 units are "frozen" in the solid state and are best described as (XeF 5 + F ) 4
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  • Uses Argon and helium are used in the welding, cutting, and spraying of metals; used in metallurgy as a protective gas. Neon: high-voltage tubular lamps Argon: mixture with nitrogen, used as filler gas for conventional light bulbs
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  • Uses Krypton: used as a better filler gas for high-quality light bulbs, also in halogen lamps Xenon: gas-discharge lamps, are used as filler gases for lamps, sometimes as constituents of gas mixtures High-purity gases are required for these applications.
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  • Uses Helium: (1997 Europe) Low-temperature technology 36 % Welding, cutting14 % Optical fibers 8 % Breathing mixtures, diving 6 % Analysis14 % Leak detection 9 % Balloons 7 % Other uses 6 %
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  • Group 18The Noble Gases The Group18 elements are called the noble gases. This is because they rarely combine with other elements and are found only as uncombined elements in nature. Their reactivity is very low.
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  • Group 18The Noble Gases Helium is less dense than air, so its great for all kinds of balloons. Helium balloons lift instruments into the upper atmosphere to measure atmospheric conditions.
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  • Group 18The Noble Gases Even though hydrogen is lighter than helium, helium is preferred for these purposes because helium will not burn.
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  • Uses for the Noble Gases The neon lights you see in advertising signs can contain any of the noble gases, not just neon. Electricity is passed through the glass tubes that make up the sign.
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  • Uses for the Noble Gases The electricity causes the gas to glow. Each noble gas produces a unique color. Helium glows yellow, neon glows red-orange, and argon produces a bluish-violet color.
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  • Uses for the Noble Gases Argon, the most abundant of the noble gases on Earth, was first found in 1894. Krypton is used with nitrogen in ordinary lightbulbs because these gases keep the glowing filament from burning out. Krypton lights are used to illuminate landing strips at airports, and xenon is used in strobe lights and was once used in photographic flash cubes.
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  • Uses for the Noble Gases At the bottom of the group is radon, a radioactive gas produced naturally as uranium decays in rocks and soil. If radon seeps into a home, the gas can be harmful because it continues to emit radiation. When people breathe the gas over a period of time, it can cause lung cancer.
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  • Group 18/0 The Noble gases Some facts 1) All of the noble gases have a full outer shell, so they are very _____________ 2) They all have low melting and boiling points 3) They exist as single atoms rather then diatomic molecules 4)Helium is lighter then air and is used in balloons and airships (as well as for talking in a silly voice) 5)Argon is used in light bulbs (because it is so unreactive) and argon, krypton and neon are used in fancy lights